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FDA and OMB say the pace isn't unusual given the complicated nature of the rules

Most of the provisions in a landmark food safety law which passed 16 months ago still haven't gone into effect and are stuck in a rule-making process at the White House, four months overdue.

That leaves 80% of the U.S. food supply operating largely under safety laws dating from the Great Depression, and safety advocates and the food industry alike are puzzled.

"It's still unclear what's holding them up," said Chris Waldrop, who directs food policy for the Consumer Federation of America.

The FDA Food Safety Modernization Act was signed by President Obama on January 4, 2011. It allows the Food and Drug Administration to take action to prevent outbreaks, increase the number of inspections and mandate recalls.

Many of the provisions, however, haven't been implemented because the White House Office of Management and Budget hasn't released the rules which the law created, which were due on January 4, 2012.

"We are back basically operating mostly under the law that is 70 years old because the new protections, the new safeguards in these rules have not been put in place," said Erik Olson, director of food programs for the Pew Health Group. "We are very worried all the effort that was put into this by all of these Democrats and Republicans and independents in Congress by the business community and the health community will really be for naught if we don't move forward with these protections."

The FDA defended the speed of the review.

"These are four big rules that set a framework for a really important change for food safety," said Michael Taylor, deputy commissioner for Foods at the FDA. "Each rule is complicated in its own right; they also have many interconnections."

The agency also points to parts of the law that have gone into effect, like the ability to hold food that may have been adulterated or mis-branded and requiring companies importing food to let the FDA know whether another country refused to allow it in.

"If you look at normal standards for how long it takes to get rules out, it hasn't taken very long at all," Taylor said. "I'm proud of this process and the pace of the work."

But food industry lobbyists and safety advocates contacted by CNN say it may have more to do with politics.

"I think it's an administration criticized for being involved in the nanny state. They're worried about that," said one lobbyist who has been in White House meetings and spoke on the condition his name would not be used. "I do think there is some concern. Will the Grocery Manufactures Association and others who stood with the president turn on him?"

The White House says this is about making good rules, not playing politics.

"The administration is working as expeditiously as possible to implement this legislation we fought so hard for," said Moira Mack, OMB spokeswoman. "When it comes to rules with this degree of importance and complexity, it is critical that we get it right."

The Centers for Disease Control and prevention estimates that one in six Americans gets sick from consuming contaminated foods or beverages. Foodborne diseases cause about 128,000 hospitalizations and 3,000 deaths each year, the CDC estimates.